When you’re 80 years old, go outside at night and look at the stars in the handle of the Big Dipper. The light from those stars left them the day you were born. Now go farther out: if Betelgeuse, 500 LY away, went supernova today, we wouldn’t know about it for another 500 years. It takes light time to travel across the Universe. The farther out in space we look, the farther back in time we look. The supernova explosion seen in the Large Magellanic Cloud in 1987 had actually happened 160,000 years ago. And the image of the Andromeda Galaxy we see now is what that galaxy looked like 2 ½ million years ago. What does it look like now? Couldn’t say. We’ll know though, about 2 and a half million years from now! This phenomenon is called Look Back Time. On the one hand it’s a problem, because we can’t know for sure what the far-away parts of the Universe look like right now. But it’s also a way to find out what the early Universe was like, because the light from so long ago is only just now reaching our eyes.